The invention relates to optical detectors or optical detector arrays, and more specifically to infrared detectors or detector arrays having high sensitivity and utilizing photothermal principles.
Optical detectors or detector arrays are typically of two types, the first type being based on photoelectric principles and the second type being based on thermal principles. The first type of optical detector includes photodiodes, photomultipliers, and the like. These detectors utilize quantum mechanical processes involving separation of charge due to absorption of a photon. The second type of optical detector includes pyroelectric detectors and thermistors. These detectors utilize all types of couplings in which a temperature change causes a direct change in voltage, resistance or capacitance.
There is a generally recognized need for a highly sensitive, broadband optical or infrared detector or detector array both in government and in industry. Utilizing conventional thermal detectors, high sensitivity can be achieved at certain wavelength ranges in the infrared region by using detectors operated at cryogenic temperatures, one example being a Ge-Cu detector which operates at 1.4.degree. K. Alternatively, pyroelectric detectors can be utilized; however, these have reduced sensitivity and relatively flat wavelength response. There is a need today for optical detectors which have high sensitivity, broad wavelength responses, can be operated at room temperature (10.degree.-40.degree. C.) and can be easily fabricated into detector arrays. The optical detector provided by the invention meets these needs.